What Is a Unix Timestamp (Epoch Time)?
A Unix timestamp, also called epoch time, is the number of seconds that have elapsed since January 1, 1970, 00:00:00 UTC, the Unix epoch. This unix timestamp converter, a unix time converter and epoch time converter in one, reads that number (or a human-readable date) and shows every common representation at once: ISO 8601, UTC string, local time, and a full breakdown into year, month, day, hour, minute, second, and millisecond. Use it to go from timestamp to date instantly, or as an epoch converter in the other direction: it works as a way to convert timestamp to date online, and just as easily in reverse, paste a date and get the corresponding epoch time back.
Seconds vs. Milliseconds: The Most Common Timestamp Bug
Unix timestamp seconds vs milliseconds confusion is probably the single most common timestamp bug in real code. The Unix standard is seconds since the epoch, but JavaScript's Date.now() and many APIs return milliseconds instead, exactly 1000 times larger. Pasting a millisecond timestamp into code expecting seconds produces a date far in the future (or the reverse, a seconds timestamp read as milliseconds lands somewhere in 1970). This tool auto-detects which unit you meant based on magnitude, so pasting either one produces the correct date without manual conversion.
The Year 2038 Problem Explained
Many older systems store Unix timestamps as a signed 32-bit integer, which overflows at 2,147,483,647 seconds after the epoch, corresponding to 03:14:07 UTC on January 19, 2038. Past that instant, a 32-bit signed timestamp wraps around to a large negative number, which typically gets interpreted as a date in 1901. This is the unix timestamp year 2038 problem, the timestamp equivalent of Y2K, and it still affects some embedded systems, older databases, and 32-bit software today. Modern systems generally use 64-bit timestamps, which don't overflow for billions of years, but the boundary is still worth testing against explicitly.
Unix Timestamps and Timezones
Unix timestamp timezone confusion comes from a common misunderstanding: a Unix timestamp itself has no timezone, it's a single, unambiguous instant in UTC. The timezone only enters the picture when that instant is displayed as a human-readable date; the same timestamp shown in New York, London, and Tokyo will show three different clock times, but they all refer to the exact same moment. This tool's world clock view shows that directly, the same underlying timestamp rendered simultaneously across 13 major timezones.
What This Tool Does Not Do
This tool converts timestamps and dates, it doesn't perform date arithmetic (adding days, calculating a difference between two dates) as its primary function; dedicated date-math tools handle that better. It also doesn't account for leap seconds, Unix time counts elapsed seconds ignoring leap seconds entirely by design, which is why Unix time is not a perfectly uniform measure of elapsed physical time, a deliberate tradeoff for simplicity that the POSIX standard makes explicit. Nothing entered here is uploaded; conversion happens entirely in your browser.